Method and apparatus for soldering and soldering land of a printed circuit board

ABSTRACT

A pair of soldering irons are fixed to a sliding plate at a predetermined interval. The soldering irons are integrally moved so as to reciprocate in a rectangular direction relative to a conveyor belt. One of the soldering irons is conveyed to a working position of the conveyor belt and the other of them is separated from the conveyor belt. While one of the soldering irons solders a circuit board, the other is cleaned. The circuit board has a slit into which a metal plate is inserted and soldered. For the slit, a soldering land constituted of a main-land and a sub-land is provided. The main-land is formed along one of longer sides of the slit. The sub-land is elongated from the main-land along a shorter side of the slit. The soldering land is not formed all around the slit so that the slit is not closed by solder when the circuit board is dip-soldered.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus for solderingfor a work conveyed to a predetermined working position by usingsoldering irons. Further, the present invention relates to a solderingland of a printed circuit board having a slit which is formed forinserting a metal plate.

2. Description of the Related Art

In a conventional soldering method, a soldering iron is disposed above amanufacturing line by which printed circuit boards are successivelyconveyed. On the printed circuit board, circuit components are mounted.The soldering iron descends toward the printed circuit board conveyed toa predetermined working position and soldering is automaticallyperformed, supplying solder to a tip of the heated soldering iron. Inthis method, if oxidized solder gathers around the iron tip, solderingperformance is greatly lowered. Therefore, an air blow is carried out toclean the iron tip once in five to twenty times of the soldering.

As to the above method, working of the soldering is interrupted whilecleaning is carried cut. Thus, operating efficiency of equipment is low.Further, upon carrying out the cleaning by the air blow, temperature ofthe iron tip lowers. Accordingly, there arises a problem in that poorsoldering is frequently performed just after the cleaning of the irontip. Moreover, when the cleaning is carried out once in a plurality oftimes of the soldering, the soldering is performed in a state that newsolder is supplied to the iron tip with old solder thereon until thenext cleaning step is carried out. Accordingly, it is difficult to keepthe solder of the iron tip at a constant amount. In view of this, thereis a fear that uniform soldering is not performed.

By the way, when a circuit board is manufactured, dip soldering isperformed in the following manner. Metal pins of electronic parts areinserted into holes formed in the circuit board on which wiring isprinted. A face of the printed circuit board, from which the metal pinsproject, is dipped in a tub containing the solder melted by a heater.Then the metal pins are soldered together.

On the other hand, for circuit components protruding from the printedcircuit board, a metal plate is provided in order to increase strengthof its attachment by enlarging a soldering area. This metal plate isinserted into a slit formed in the printed circuit board after theprinted circuit board was dip-soldered. The slit has a soldering landformed all around the slit. After insertion of the metal plate, themetal plate is soldered.

However, as shown in FIG. 5A, if a soldering land 81 is formed allaround a slit 80, the slit 80 is sometimes closed by tension of solder82 adhering to the soldering land 81 when the dip soldering isperformed. The state that the slit 80 is closed with the solder is shownin FIG. 5B.

Moreover, as shown in FIG. 6A, when a soldering land 91 is formed halfaround the slit 80 in order to prevent from closing the slit 80, theslit 80 is not closed by the dip soldering. However, when a metal plate93 is inserted into the slit 80 and soldered, the solder hardly goesround to the other side of the slit 80 where the soldering land does notexist. Thus, there arises a problem in that unsatisfactory solderingtends to be performed and sufficient strength is not obtained.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a primary object of the presentinvention to provide a soldering method and apparatus in which operatingefficiency of equipment is improved and good soldering is performed.

It is a second object of the present invention to provide a solderingmethod and apparatus in which uniform soldering is performed.

It is a third object of the present invention to provide a solderingland of a printed circuit board in which a slit formed in the printedcircuit board is prevented from being closed when dip soldering isperformed.

It is a fourth object of the present invention to provide a solderingland of a printed circuit board in which it is possible to perform goodsoldering for a metal plate inserted into a slit formed in the printedcircuit board.

In order to achieve the above and other objects, the soldering methodand apparatus according to the present invention comprises a pluralityof soldering irons fixed to a sliding plate at a predetermined interval.Further, the soldering land according to the present invention comprisesa main-land and a sub-land.

In a preferred embodiment, The soldering irons and the sliding plate areintegrally moved by a plunger which is fixed to one end of the slidingplate. The soldering irons reciprocate by a predetermined distance in arectangular direction relative to a conveyor belt. One of the solderingirons is moved to a working position where soldering is performed for awork put on the conveyor belt. At the same time, the other of thesoldering irons is separated from the working position and moved to acleaning position. While one of the soldering irons solders for thework, the other of them is cleaned at the cleaning position by a nozzleshooting air.

The soldering land according to the present invention is constituted ofthe main-land and the sub-land. The main-land is formed along only oneof longer sides of the slit formed in the printed circuit board. Thesub-land is elongated from the main-land along a shorter side of theslit. The soldering land is not formed all around the slit so thatsolder does not spread over the slit when dip soldering of the circuitboard is performed. Accordingly, the slit is prevented from beingcovered with the solder. After the dip soldering, the metal plate isinserted into the slit and soldered. When the metal plate is soldered,the solder adheres to the metal plate along not only the main-land butalso the sub-land. Thus, great strength for soldering the metal plate isobtained.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomeapparent from the following detailed description of the preferredembodiments of the invention when read in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view of a soldering apparatus according to thepresent invention;

FIGS. 2A, 2B and 2C are explanatory illustrations of a soldering landaccording to the present invention;

FIG. 3 is a plan view of a printed circuit board provided with thesoldering land;

FIG. 4 is an explanatory illustration of another soldering land;

FIGS. 5A and 5B are explanatory illustrations of a conventionalsoldering land; and

FIGS. 6A and 6B are explanatory illustrations of another conventionalsoldering land.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Referring to FIG. 1, an embodiment according to the present invention isdescribed. On a conveyor belt 10, work holders 11 are successivelydisposed at an unfixed interval. The work holder 11 holds a work 12 forwhich soldering is performed. The conveyor belt 10 moves intermittentlyin a direction represented by an arrow shown in FIG. 1. The work 12 isconveyed to a predetermined position in order. At the predeterminedposition, the soldering is performed by a soldering apparatus. The workholders 11 may be successively disposed on the conveyor belt 10 at aconstant interval. In this case, the conveyor belt 10 is intermittentlymoved in a fixed cycle.

Structure of the soldering apparatus according to the present inventionis described below. Posts 15 and 16 are disposed at symmetric positionsrelative to the conveyor belt 10. A base member 17 is fixed to the posts15 and 16 in a rectangular direction relative to the conveyor belt 10.The base member 17 is provided with a sliding plate 20 which is slidablein a horizontal direction. The sliding plate 20 is provided with a pairof soldering irons 23 and 24 disposed at a predetermined interval. Thesoldering iron 23 is fixed to a plunger of a cylinder 39 for moving thesoldering iron 23 in up-and-down direction. The soldering iron 24 isfixed to a plunger of a cylinder 40 for moving the soldering iron 24 inup-and-down direction. The cylinders 39 and 40 are fixed to the slidingplate 20.

A cylinder 25 is attached to the base member 17 and a plunger of thecylinder 25 is fixed to one end of the sliding plate 20. The cylinder 25constitutes a moving means of the soldering irons 23 and 24. The movingmeans reciprocates the soldering irons 23 and 24 by a predetermineddistance in a rectangular direction relative to the conveyor belt 10.Either of the soldering irons 23 and 24 is set at the working positionof the conveyor belt 10 by the moving means. Reciprocation of thesliding plate 20 is carried out by the cylinder 25 every time ofsoldering. Thus, the soldering irons 23 and 24 are set at the workingposition of the conveyor belt 10 one after the other every time ofsoldering.

Supplying ports of tubes 27 and 28 are respectively disposed near eachtip of the soldering irons 23 and 24. The necessary solder for solderingof one time is sent from a solder supplying device (not shown) andautomatically supplied to each tip of the soldering irons 23 and 24 fromthe supplying ports of the tubes 27 and 28. The tubes 27 and 28 arerespectively fixed to each end portion of holding members 29 and 30.

Other end portions of the holding members 29 and 30 are respectivelyattached to each of linear guides 29a and 30a which are fixed to thesliding plate 20. These end portions are slidable in up-and-downdirection. The holding members 29 and 30 are respectively fixed to eachof the soldering irons 23 and 24. Thus, the soldering iron 23 and thetube 24 are integrally moved with the tubes 27 and 28. The supplyingports of the tubes 27 and 28 are always; disposed near the solderingirons 23 and 24 respectively so that optimum supply of the solder isadapted to be performed.

Nozzles 34 and 35 constituting a cleaning means are disposed atsymmetric positions relative to the conveyor belt 10. The nozzles 34 and35 shoot air sent by an air compressor or the like (not shown) from itsshooting ports. By shooting air, the nozzle removes the solder remainingaround the tip of the soldering iron separated from the working positionof the conveyor belt 10. The nozzle cleans one of the soldering irons 23and 24 while the other of the soldering irons 23 and 24 performs thesoldering. Under the nozzles 24 and 25, vessels 36 and 37 arerespectively provided to collect the swept solder.

An operation of the above-mentioned soldering apparatus is describedbelow. By moving the sliding plate 20, the soldering iron 23 is moved tothe predetermined working position of the conveyor belt 10. At thistime, the soldering iron 24 is separated from the conveyor belt 10 andmoved to an above position of the vessel 37. When the work 12 isconveyed to the predetermined position, the soldering iron 23 heated ata prescribed temperature is descended by means of the cylinder 39. Thesoldering iron 23 contacts the work 12 to perform soldering.

At the same time, the soldering iron 24 is descended into the vessel 37by means of the cylinder 40. while the soldering iron 23 performssoldering, air is shot at the tip of the soldering iron 24 from thenozzle 35 so that cleaning thereof is carried out. By shooting air, thesolder remaining on the tip of the soldering iron 24 is away. The sweptsolder is corrected in the vessel 37. As the cleaning is carried out inthe vessel 37, dispersion of the solder due to air blow is prevented.

When the soldering and the cleaning of the soldering irons 23 and 24 areover, the cylinders 39 and 40 raise the soldering irons 23 and 24respectively. After the soldering iron 23 was separated from the work 12and the soldering iron 24 was drawn out of the vessel 37, the slidingplate 20 is moved in left direction in FIG. 1 by means of the cylinder25. The cleaned soldering iron 24 is conveyed to the working position ofthe conveyor belt 10. The used soldering iron 23 is separated from theconveyor belt 10 and moved to the above position of the vessel 36.

When the next work 12 is conveyed to the predetermined position, thecylinder 40 lowers the soldering iron 24 toward the work 12 to performthe soldering. At the same time, the cylinder 39 lowers the solderingiron 23 into the vessel 36. While the soldering is performed by thesoldering iron 24, air is shot at the soldering iron 23 from the nozzle34 to remove the solder remaining on the tip thereof.

When the soldering and the cleaning of the soldering irons 23 and 24 areover, the soldering iron 24 is separated from the work 12 by means ofthe cylinder 40 and the soldering iron 23 is drawn out of the vessel 36.Successively, the sliding plate 20 is moved in right direction in FIG. 1by means of the cylinder 25. The cleaned soldering iron 23 is conveyedto the working position of the conveyor belt 10. The used soldering iron24 is separated from the conveyor belt 10 and moved to the aboveposition of the vessel 37. The process described above is repeated.

By the way, when the cleaning of the soldering iron is carried out bythe air blow, the temperature of the tip thereof lowers. However, thetemperature of this soldering iron rises up to the prescribedtemperature at which good soldering is performed during the movement tothe working position of the conveyor belt. Accordingly, it is preventedthat poor soldering is performed due to a drop of the tip temperaturecaused by the cleaning of the air blow. Moreover, while one of thesoldering irons performs the soldering, the cleaning of the other iscarried out so that there is no waiting time and it is possible toachieve a high operating efficiency of equipment. Further, the cleaningof the soldering iron is carried out every time of the soldering so thatthe constant amount of solder adheres to the tip of the soldering iron.Accordingly, uniform soldering may be performed.

In the above-described embodiment, the plunger of the cylinder is fixedto each of soldering irons to move the soldering iron in up-and-downdirection individually. However, it is possible to move the slidingplate in up-and-down direction together with the base member. In thiscase, the base member is slidably attached to the posts and a plunger ofa cylinder is fixed to each of both ends of the base member to move thebase member in up-and down direction. Moreover, in the above-describedembodiment, the sliding plate and the soldering iron are moved by usingthe cylinder. However, this is not exclusive, for example, a gear trainor a cam mechanism may be employed. Further, for the cleaning of thesoldering iron, instead of the air blow, it is possible to adopt amethod in which the solder is swept by using a roller, cleaning tape, orbrush.

As described above, a pair of the soldering irons disposed at thepredetermined interval are integrally moved and solder the work conveyedto the predetermined position. The soldering irons are used one afterthe other. Further, while one of the soldering irons performs thesoldering, the other is cleaned. Accordingly, loss of time due tocleaning is prevented and it is possible to achieve the high operatingefficiency of equipment. The cleaning of the soldering iron is carriedout every time of the soldering so that the amount of the solderadhering to the tip of the soldering iron is kept at constant. Thus, itbecomes possible to perform the uniform soldering.

Next, referring to FIGS. 2 to 4, another embodiment according to thepresent invention is described.

FIG. 3 shows a printed circuit board provided with a soldering landaccording to the present invention. In the printed circuit board 52,holes 53 and slits 54 are formed. The hole 53 is for inserting arod-like metal pin of electrical parts and so forth. The slit 54 is forinserting a metal plate 57 which is attached to large-sized circuitcomponents of a switch, a battery holder and so forth. Soldering lands55 and 56 are formed around the hole 53 and the slit 54 respectively.

Dip soldering is performed for the printed circuit board 52 after thepins of the electrical parts or the like have been inserted into theholes 53. The soldering land 55 is provided all around the hole 53 sothat the solder adheres all around the pin inserted into the hole 53.

As shown in FIGS. 2A, 2B and 2C, an outline of the slit 54 isconstituted of longer sides 54a and 54b, and arc-shaped shorter sides54c and 54d connected to the longer sides 54a and 54b. Of course, theshorter side may be linear. The soldering land 56 is constituted of amain-land 56a and a sub-land 56b. The main-land 56a is provided alongthe longer side 54a. The sub-land 56b is formed so as to be elongatedfrom the main-land 56a along the shorter side 54c and go round to theother longer side 54b.

Referring to FIGS. 2A, 2B and 2C, it is described that the circuitcomponent having the metal plate is soldered to the printed circuitboard provided with the above soldering land. When the pins of theelectrical parts are inserted into the holes 53 and dip-soldered, solder60 adheres to the soldering land 56. At this time, as the soldering land56 does not surround all around the slit 54, the tension of the solder60 is diagonally applied due to the main-land 56a and the sub-land 56b.Thus, the solder 60 does not spread over the slit 54 so that the slit 54is prevented from being closed by the dip soldering.

Successively, the metal plate 57 is inserted into the slit 54 andsoldered. The solder 60 adheres to the main-land 56a and the sub-land56b. As the sub-land 56b is formed such as to go round to the otherlonger side 54b, the solder 60 goes round to the sub-land 56b side ofthe metal plate 57 besides the main-land 56a side thereof. Accordingly,sufficient strength is obtained.

Another shape of the soldering land according to the present inventionis illustrated in FIG. 4. A soldering land 66 shown in FIG. 4 isconstituted of a main-land 66a and sub-lands 66b and 66c. The main-land66a is provided along the longer side 54a of the slit 54. The sub-lands66b and 66c are formed such that an upper portion aid a lower portion ofthe main-land 66a are elongated along the shorter sides 54c and 54d. Thesub-lands 66b and 66c go round to the other longer side 54b. Similareffect to the above embodiment is obtained.

Moreover, in the above-described embodiments, the sub-land is formedsuch that the main-land provided along one of the longer sides of theslit is elongated along the shorter side of the slit and go round to theother longer sides. However, the sub-land is not exclusive to this. Thesub-land may be formed so as to be elongated in a separate directionfrom the other longer side.

As described above, the soldering land is constituted of the main-landformed along one of the longer sides of the slit and the sub-landelongated from the main-land along the shorter side of the slit.Accordingly, the solder adhering to the soldering land does not spreadover the slit so that the slit is not closed. Further, when the metalplate is inserted into the slit and soldered, the solder goes round fromthe main-land to the sub-land. Accordingly, the solder adheres to notonly the metal plate face of the main-land side but also the metal plateface of the sub-land side so that the great strength of the soldering isobtained.

In the above-described first embodiment, the movable member, namely, thesliding plate 20 reciprocates in a straight line. However, the movablemember may be rotatable or swingable. For example, a movable armrotating around a center thereof is used. One end of the arm ispositioned above the conveyor belt and the other end thereof isseparated from the conveyor belt. A first soldering iron is attached toone end of the arm and a second soldering iron is attached to the otherend thereof. When the first soldering iron is set at the workingposition for soldering for the work put on the conveyor belt, the secondsoldering iron is separated from the conveyor belt and set at thecleaning position where an air nozzle and a vessel are disposed. Uponrotating the arm by 180 degrees, the second soldering iron moves to theworking position and the first soldering iron is separated from theconveyor belt to be set at the cleaning position. The center of the armmay be positioned not only above the conveyor belt but also away fromthe conveyor belt. Moreover, stop position of the arm may be a positioncrossing the conveyor belt diagonally besides a rectangular positionrelative to the conveyor belt. Further, instead of rotating the arm in asame direction every 180 degrees, the arm may be alternately rotated inboth directions every 180 degrees. Besides the arm, it is possible touse a disk or a sector.

Although the present invention has been fully described by way of thepreferred embodiments thereof with reference to the accompanyingdrawings, various changes and modifications will be apparent to thosehaving skill in this field. Therefore, unless otherwise these changesand modifications depart from the scope of the present invention, theyshould be construed as included therein.

What is claimed is:
 1. A soldering land of a printed circuit boardhaving a slit into which a metal plate is inserted and soldered afterdip soldering has been performed for said printed circuit board, saidsoldering land comprising:a mainland formed along only one of longersides of said slit; and at least one sub-land elongated from saidmain-land and formed along at least one of shorter sides of said slit,wherein said soldering land prevents solder from closing the slit duringthe dip soldering, and after the metal plate is inserted into the slit,facilitates the soldering of the metal plate to the printed circuitboard.
 2. A soldering land of a printed circuit board according to claim1, wherein said sub-land is formed so as to go round to the other ofsaid longer sides of said slit.
 3. A soldering land of a printed circuitboard according to claim 1, wherein a number of said sub-lands is twoand said sub-lands are formed along both of said shorter sides of saidslit.
 4. A soldering land of a printed circuit board according to claim1, wherein said shorter side has an arc-like shape.